Latent pseudorabies virus infection in medulla oblongata from quarantined pigs
Latent pseudorabies virus infection in medulla oblongata from quarantined pigs
复制标题
隔离猪延髓潜伏性伪狂犬病病毒感染
DOI：
10.1111/tbed.13712
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发表时间：
2020-07-14
影响因子：
4.3
通讯作者：
Wang, Xiao-Jia
中科院分区：
文献类型：
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作者：
Lu, Jin-Jin;Yuan, Wan-Zhe;Wang, Xiao-Jia
伪狂犬病病毒（PRV）是养猪业的主要病原体，也是对人类健康的威胁。潜伏PRV感染的猪终生携带病毒，并且在有利条件下可以被激活。这对控制病毒构成了非常重要的挑战，甚至可能阻止其消除。为了调查野生型PRV的潜伏感染以及由于在农场使用减毒活疫苗引起的感染，追踪了来自两个大规模养猪场的80头猪。在6个月大时，屠宰检疫猪并收集脑样品。建立了一种以gB和gE基因为靶基因的PCR检测方法，用于检测延髓中PRV的DNA片段。其中5份（6.3%）为gB和gE基因片段双阳性，60份（75%）为gB单阳性，15份（18.7%）为双阴性。在gB基因片段阳性标本中发现了一部分潜伏相关转录本（latency-associated transcripts，LAT）EP 0 mRNA。此外，5个双阳性样本进行盲传，在第四代的5个样本中，有3个样本出现明显的细胞病变效应。经Western blotting、PCR和测序鉴定，其中2株分离病毒与疫苗株Bartha-K61相关。另一株与国内流行株HN 1201和LA亲缘关系较近，与亚洲其他分离株关系相对不密切。这些结果表明，活疫苗以类似于野生型PRV的方式潜伏存在于脑中，这在养猪业中造成了潜在的安全问题。在猪中发现了伪狂犬病病毒和活疫苗病毒共存，表明活疫苗不能提供完全的灭菌免疫，这可能解释了接种疫苗的农场中伪狂犬病的爆发。
Pseudorabies virus (PRV) is a major pathogen in pig husbandry and is also a risk to human well-being. Pigs with latent PRV infection carry the virus lifelong, and it can be activated under conducive conditions. This poses a very important challenge to the control of the virus and may even prevent its elimination. To investigate latent infection with wild-type (wt) PRV, and also infection due to the use of live attenuated vaccines on farms, 80 pigs from two large-scale swine operations were traced. At 6 months old, the quarantined pigs were slaughtered and brain samples were collected. A PCR assay targeting the gB and gE genes was developed to detect PRV DNA fragments in medulla oblongata. Five of the samples (6.3%) were gB and gE gene fragment double-positive, 60 of the samples (75%) were gB single-positive, and 15 samples (18.7%) showed double-negative. A portion of latency-associated transcripts (LATs), EP0 mRNA, were found to be present in the gB gene fragment positive samples. Furthermore, the five double-positive samples were transmitted blindly, and apparent cytopathic effects were found in three of the five samples in the fourth generation. By means of Western blotting, PCR and sequencing, two of the isolated viruses were found to be related to vaccine strain Bartha-K61. Another was closely related to domestic epidemic strains HN1201 and LA and relatively unrelated to other Asian isolates. These results suggest that the live vaccines are latently present in brains, in a manner similar to wt PRV, and this poses potential safety issues in the pig husbandry industry. Wt PRV and live vaccine viruses were found to co-exist in pigs, demonstrating that the live vaccines were unable to confer complete sterilizing immunity, which may explain outbreaks of pseudorabies on vaccinated farms.